DGM (Omega) NPB filter question

Late last summer I purchased a 1.25" DGM NPB filter. I used it a couple of weeks ago and when I was putting it back on its case I noticed the filter element was a little loose in the frame and was rattling a bit. I don't recall it being loose before, but it may have been. I didn't think much about it until I received a 2" version of the filter from Omega Filters this weekend and the filter element in that one is a little loose too. Does anyone know if this is normal? Maybe for glass expansion or something? Or should I tighten up the retaining ring a little bit?

Late last summer I purchased a 1.25" DGM NPB filter. I used it a couple of weeks ago and when I was putting it back on its case I noticed the filter element was a little loose in the frame and was rattling a bit. I don't recall it being loose before, but it may have been. I didn't think much about it until I received a 2" version of the filter from Omega Filters this weekend and the filter element in that one is a little loose too. Does anyone know if this is normal? Maybe for glass expansion or something? Or should I tighten up the retaining ring a little bit?

Thanks.

It sounds like the retaining ring is just a little loose (perhaps from vibration during shipping or after some use due to wide temperature variations). You can tighten it up a little with an optical spanner, but just snug it "finger tight" and not really hard and fast tight, as that might distort the glass. I have an Orion Skyglow filter that does the same thing, as the retaining ring keeps loosening up over time (annoying, but I can snug it up with a simple tool from time to time). Clear skies to you.

Dave, thanks for the response. I went a head and snugged up the retaining ring till they stopped rattling. I called Omega about this yesterday afternoon and received a call back today. They said the same thing.

I just received a "DGM Optics Nebula Astronomy Filter" from a omegabob2 on ebay $75.00 which was represented as "New: A brand-new, unused, unopened, undamaged item in its original packaging". It came in a scratched up plastic enclosure like it has been at the bottom of someone's eyepiece case for years, the filter has no DGM Optics markings on it, the filter itself is a plastic holder with a plastic snap ring and worse the filter is loose in the holder. This could never be used in a CCD arrangement becasue one could not do optical flats with it since it moves. I found a review of DGM Optics on Cloudy Nights http://www.cloudynig...hp?item_id=1578 and they show a metal housing as well as engraved filter information. What I received was not a DGM Optics filter! So I would check your filter and see if it is a knock-off. I am sending mine back if I can. Anyone know where I can get a real DGM Optics filter?

Well that is sort of disconcerting! Perhaps it is a mistake on their part as I believe they also sell blemished items. You should contact them and if need be use the powers of ebay to have it made right. The one good thin about the bay is that their policies are almost totally skewed towards the buyers side, which is one reason I don't sell on there anymore.

I also just saw you can now buy directly from DGM through their webpage. I hope when you do that you get a new one.

Sorry for your troubles. Unfortunately that was a genuine DGM Optics filter that you received from Omega`s E-bay site. I also have informed them (Omega) of this issue, and have been trying to be alert for continued problems.

Though Omega does have a few retail dealers, they are the only authorized direct retailer, and manufacturer, of my original designs.

Since around April I started selling them directly via my own website. As mentioned in other posts on CN, I package them in a sturdy 5x5x5 cardboard box. Each filter is contained in a captive-top "calm-shell" holder. I don`t label the container, but the filters are of course marked appropriately on the rings. S&H is free in the lower US.

I don`t want to disparage anyone from ordering my filters from your retail source of choice, but if you have any doubts I would recommend ordering direct through DGM Optics.

Sorry for your troubles. Unfortunately that was a genuine DGM Optics filter that you received from Omega`s E-bay site. I also have informed them (Omega) of this issue, and have been trying to be alert for continued problems.

Though Omega does have a few retail dealers, they are the only authorized direct retailer, and manufacturer, of my original designs.

Since around April I started selling them directly via my own website. As mentioned in other posts on CN, I package them in a sturdy 5x5x5 cardboard box. Each filter is contained in a captive-top "calm-shell" holder.

What's the best way to clean an NPB filter? Mine has what looks like a bit of fingerprint near the edge.Thx,

Same as eyepieces for me, I just use the Zeiss wipes that you can find at Walmart. They work great!

I`d second that, but add that it might be advisable to try and remove the fingerprint before using the wipes. Just put a very small amount of isopropanol on a q-tip and gently rub first with the iso side of the q-tip, then the dry side to remove standing fluid from the surface. Repeat as needed. Then go for the wipes.

"Sorry for your troubles. Unfortunately that was a genuine DGM Optics filter that you received from Omega`s E-bay site. I also have informed them (Omega) of this issue, and have been trying to be alert for continued problems."

"Sorry for your troubles. Unfortunately that was a genuine DGM Optics filter that you received from Omega`s E-bay site. I also have informed them (Omega) of this issue, and have been trying to be alert for continued problems."

Thanks...Eric

Hi Eric,

No, it was a "genuine" NPB in that it is the same filter I get from Omega, and they sell via eBay, using my original designs.

I was more addressing the issue of packaging, and the holders, just to say I am aware of the problem with some of the filters Omega has shipped. And that if they are ordered via DGM Optics they will arrive in new holders. I also check the retainer rings to be sure they are tight when I ship.

What's the best way to clean an NPB filter? Mine has what looks like a bit of fingerprint near the edge.
Thx,

Same as eyepieces for me, I just use the Zeiss wipes that you can find at Walmart. They work great!

I`d second that, but add that it might be advisable to try and remove the fingerprint before using the wipes. Just put a very small amount of isopropanol on a q-tip and gently rub first with the iso side of the q-tip, then the dry side to remove standing fluid from the surface. Repeat as needed. Then go for the wipes.

"Sorry for your troubles. Unfortunately that was a genuine DGM Optics filter that you received from Omega`s E-bay site. I also have informed them (Omega) of this issue, and have been trying to be alert for continued problems."

Thanks...Eric

Hi Eric,

No, it was a "genuine" NPB in that it is the same filter I get from Omega, and they sell via eBay, using my original designs.

I was more addressing the issue of packaging, and the holders, just to say I am aware of the problem with some of the filters Omega has shipped. And that if they are ordered via DGM Optics they will arrive in new holders. I also check the retainer rings to be sure they are tight when I ship.

What's the best way to clean an NPB filter? Mine has what looks like a bit of fingerprint near the edge.
Thx,

Same as eyepieces for me, I just use the Zeiss wipes that you can find at Walmart. They work great!

I`d second that, but add that it might be advisable to try and remove the fingerprint before using the wipes. Just put a very small amount of isopropanol on a q-tip and gently rub first with the iso side of the q-tip, then the dry side to remove standing fluid from the surface. Repeat as needed. Then go for the wipes.

"Sorry for your troubles. Unfortunately that was a genuine DGM Optics filter that you received from Omega`s E-bay site. I also have informed them (Omega) of this issue, and have been trying to be alert for continued problems."

Thanks...Eric

Hi Eric,

No, it was a "genuine" NPB in that it is the same filter I get from Omega, and they sell via eBay, using my original designs.

I was more addressing the issue of packaging, and the holders, just to say I am aware of the problem with some of the filters Omega has shipped. And that if they are ordered via DGM Optics they will arrive in new holders. I also check the retainer rings to be sure they are tight when I ship.

Dan,Thanks for including your website link for ordering the DGM filters. I just placed an order for the 2" GCE filter, and I'm looking forward to receiving a nice product.

I live in a place that is moderately light polluted about 40 miles SE of Phoenix, AZ and there a few HP sodium street lights near my home. I have a shield on the one closest to me, but there are a few more down the road. I am hoping this filter will help take a bit of that light pollution out of my way while viewing some galaxies. I can see Andromeda naked eye from my house on a good night of seeing, so that tells you the light pollution in my area isn't too bad and might be an optimum level for that filter. :-)Carol Sabo

Dan,
Thanks for including your website link for ordering the DGM filters. I just placed an order for the 2" GCE filter, and I'm looking forward to receiving a nice product.

I live in a place that is moderately light polluted about 40 miles SE of Phoenix, AZ and there a few HP sodium street lights near my home. I have a shield on the one closest to me, but there are a few more down the road. I am hoping this filter will help take a bit of that light pollution out of my way while viewing some galaxies. I can see Andromeda naked eye from my house on a good night of seeing, so that tells you the light pollution in my area isn't too bad and might be an optimum level for that filter. :-)
Carol Sabo

Hi Carol,

Yes the GCE should be very nice from your location. But don`t forget to try it as a general low power broadband filter. It really does a nice job with milky way dust lanes, with minimal star brightness reduction. And because it rejects the same WLs as all LPR/nebula filters it does do a nice job on many nebula, preserving a very natural view.

Don't expect a miracle. My experience is that the CGE is a filter that produces subtle improvements at best and many times makes no discernible difference in details seen. That said, I have had many times when it did improve the view by ever so slightly increasing the contrast, bringing out just a bit more detail, and creating a more pleasant view overall.

From your description of your LP situation, it sounds like you might be in the conditions where I've seen it make the most improvement. My home is a red/white zone and my usual dark site is a blue zone. When snowed out of the blue zone site I use a site in a yellow/green zone and that's were I've seen the most improvement through the use of my CGE.

Dan,Thanks for including your website link for ordering the DGM filters. I just placed an order for the 2" GCE filter, and I'm looking forward to receiving a nice product.

I live in a place that is moderately light polluted about 40 miles SE of Phoenix, AZ and there a few HP sodium street lights near my home. I have a shield on the one closest to me, but there are a few more down the road. I am hoping this filter will help take a bit of that light pollution out of my way while viewing some galaxies. I can see Andromeda naked eye from my house on a good night of seeing, so that tells you the light pollution in my area isn't too bad and might be an optimum level for that filter. :-)Carol Sabo

The NPB filter will be of some use under those conditions on emission nebulae. As for comments on the GCE filter, it works to some degree on some galaxies, but is best under dark to only very slightly light polluted conditions. Once you get to where skyglow is a somewhat more notable problem, then you may be a little better off with a regular broad-band LPR filter than you are with the GCE. The GCE does not have quite the rejection of very broad sources like HP Sodium light that a more aggressive LPR filter might. The following review of the GCE might help a bit here: